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UN NEUTRINO S’TERRE-T-IL?

This seminar discusses the status of neutrino oscillations, reactor experiments, and the possibility of a sterile neutrino. It also explores the reactor anomaly and the Gallium neutrino anomaly.

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UN NEUTRINO S’TERRE-T-IL?

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  1. UN NEUTRINO S’TERRE-T-IL? D. Lhuillier SéminaireSPhN

  2. Outline • Intro on (reactor) n • The 4thn hypothesis: • Status of the reactor anomaly • General context of other results • Testing new ne disappearance at short distance from compact sources: • Reactor experiments • Source experiments D. Lhuillier - Séminaire SPhN

  3. Neutrino Status • 3 active neutrinos. • Neutralpartner of charged leptons in weak isospin doublets. • (anti)neutrinos are (rigth) lefthanded. • Flavor eigenstates ≠ mass eigenstates + different masses. •  Neutrinos canoscillate D. Lhuillier - Séminaire SPhN

  4. Neutrino Oscillations n1, n2, n3 Interaction / flavor Propagation / mass Interaction / flavor -1 ne nm nt n1 n2 n3 ne nm nt n1 n2 n3 q q = = . . . . Dm2 12 = 33.5 ± 1.5° 23 = 40.4 ± 5° 13= 8.7 ± 0.5° m221 = 7.6 ± 0.2 10-5 eV2 m2 31| = 2.5 ± 0.1 10-3eV2 d=? D. Lhuillier - Séminaire SPhN

  5. Open questions • Neutrino masses • Absolute masses • Hierarchy • Dirac or Majorana  decay, 0ν decay, cosmo Matter effects, 0ν decay 0ν decay • CP violation • Impact on the matter-antimatter asymmetry? • Additional neutrino states? Oscillation experiments D. Lhuillier - Séminaire SPhN

  6. Reactor n D. Lhuillier - Séminaire SPhN

  7. Reactor Antineutrinos • Reactor are intense and pure sources of electron antineutrinos from b- decay of fission products ne • Few MeV energy range • 2.1020ne /s/GWth • Compensate for tiny interaction probability D. Lhuillier - Séminaire SPhN

  8. Golden Detection Process Inverse Beta Decay Selective signal sequence: e+ prompt signal + n-capture few 10 ms later Backgrounds • Accidental: [g-nth] coinc • Correlated: fast n • Not sensitive to solar ne. D. Lhuillier - Séminaire SPhN

  9. Oscillations of Reactor n n1, n2, n3 ne ne Interaction / flavor Propagation / mass Interaction / flavor Periodic disappearance of the detected ne rate with a L/E dependence P(e e) = 1 - sin2(2ij) sin2(m2ijL/4E) D. Lhuillier - Séminaire SPhN

  10. Reactor n Spectra D. Lhuillier - Séminaire SPhN

  11. Prediction of Reactor n Spectra Reference fission b spectra of 3 isotopes measured at the ILL reactor K. Schreckenbach et al., Phys. Lett. 99B, 251 (1981) • Accurate reference of total fission b-spectra • Key input for searches of oscillations at reactors D. Lhuillier - Séminaire SPhN

  12. Conversion of reference e- spectra • 1- Fit total e- spectrum with a sum of 30 effective b branches determined by iterative method (instead of ~10,000 real branches) • 2- Convert each effective e- branches to nbranches • 3- Sum all converted nbranches to get total n spectrum • Reference neutrino spectra to be coupled to a reactor simulation. • Dramatic improvement with respect to ab-initio calculation, limited by the knowledge of nuclear data. D. Lhuillier - Séminaire SPhN

  13. Detected Spectrum En ∊ [2-8] MeV sinteracion ~ qq 10-43 cm2 D. Lhuillier - Séminaire SPhN

  14. The Reactor Anomaly D. Lhuillier - Séminaire SPhN

  15. Re-evaluation of Reactor n Spectra Work triggered at CEA-Irfu by the need of accurate predictions for the Double Chooz experiment Improved conversion of ILL beta spectra Th. Mueller et al, Phys. Rev. C83,054615 (2011) P. Huber, Phys. Rev. C84, 024617(2011) New Conversion  +3.5% Accumulation of long lived isotopes  +1% D. Lhuillier - Séminaire SPhN

  16. Re-evaluation of Detected Spectra Increased prediction of detected flux New Conv.  + 1.5% New tn PRD 83, 073006 (2011) D. Lhuillier - Séminaire SPhN

  17. The Reactor ne Anomaly • Re-analysis of 19 Short Baseline Experiments (L<100m) • Observables: ratios of observed event rate to predicted rate of events • 2011 resultsPhys. Rev. D83, 073006 (2011) • Average: μ = 0.943 ± 0.023 • 98.6 % C.L. deviation from μ = 1 D. Lhuillier - Séminaire SPhN

  18. Including km-scale Experiments • Refined treatment of experimental correlations • Latest updated neutron mean life (τn = 881.5 s). • Corrects for a statistical bias (1% shift) • km-scale baselines (Chooz, Double Chooz, Palo Verde) • θ13 deficit corrected from Daya Bay’s independent measurement • μ = 0.936 ± 0.024, 2.7σdeviationfromunity D. Lhuillier - Séminaire SPhN

  19. The Sterile Neutrino Hypothesis D. Lhuillier - Séminaire SPhN

  20. A 4th neutrino ? New prediction for no oscillation Old prediction q12 New Oscillation to sterile n? Atmospheric Oscillation Solar Oscillation qnew? Reactor anomaly q13 D. Lhuillier - Séminaire SPhN

  21. The Gallium Neutrino Anomaly • Calibration of solar neutrino detectors withMCi e-capture neemitters • 71Ga/37Ar + ne → 71Ge/37Cl + e- • Gallex, <L>=1.9 m • 51Cr, 750 keV • Sage, <L>=0.6 m • 51Cr & 37Ar (810 keV) • Deficit observed • 2.8 - 3 σ anomaly • Supported by new 71Ga(3He,3H)71Ge cross section meas. Gallex D. Lhuillier - Séminaire SPhN

  22. Contours D. Lhuillier - Séminaire SPhN

  23. Contours (-) Data consistent with nedisappearance with L/E≈1 m/MeV J. Kopp et al., arXiv:1303.3011 D. Lhuillier - Séminaire SPhN

  24. Theoretical Aperçu New neutrino id • Mass of the order 1 eV • Sterile • Mixing with the active flavor(s) • L state because of Lorentz invariance 3 sterile n candidates? No Could only mix L n state with sterile L state of anti-n DNlepton= 2 Not compatible with independent L,R states of Dirac formalism • Requires new ns state(s), with Dirac or Majorana masses • Little theoretical constraints on mass range and number of ns D. Lhuillier - Séminaire SPhN

  25. Anomalous & Regular Results − − − − − − D. Lhuillier - Séminaire SPhN

  26. Appearance VS Disappearance C. Giunti et al., arXiv:1302.6720 J. Kopp et al., arXiv:1303.3011 AP DIS Hard to reconcileνe/νe appearance/disappearance withνμ/νμ disappearance (3+1 & 3+2 models) D. Lhuillier - Séminaire SPhN

  27. CMB • The recombination of e- and p ~380000 y after the big-bang provides a quasi infinite propagation to the photons • Distribution of anisotropies is frozen and observable today in the CMB Spherical harmonics expansion of the signal Position and amplitude of the acoustic peaks are sensitive to the cosmological parameters: H0, Ωbh2,Ωch2,ΩΛ, …., Neff, Σmν http://www.apc.univ-paris7.fr/blog/content/le-fond-diffus-cosmologique-cmb D. Lhuillier - Séminaire SPhN

  28. Constraintsfromcosmology Planck results, astro-ph:1303.5076 • Combination of Planck results and BAO data: • Neff<3.9 • meffs<0.6 eV 95% C.L. • Requires non-standard mechanism to depart from DNeff = +1 D. Lhuillier - Séminaire SPhN

  29. Constraintsfromcosmology See next SPP seminar by J. Lesgourges • Several tensions between data sets would require fine study of systematic errors • Overlap with reactor anomaly sensitive to choice of data sets arXiv,hep-ph:1309.3192 • Need complementary approach of direct measurements of sterile neutrino D. Lhuillier - Séminaire SPhN

  30. Testing new ne disappearance at short distance from compact sources D. Lhuillier - Séminaire SPhN

  31. Experimental Strategy • Need direct test, beyond the current mean deviation from predicted rate • Input from sterile neutrino fits • Δm2 ≈ 0.1-10 eV2→ • sin2(2θee) ≈ 0.01-0.15 • Experimental specifications: • Compact source • Good vertex and energy resolutions • High statistics, few % stat. uncertainty • Few % syst measurements to cover the anomaly contour • Search for a new oscillation pattern in E & L • Measurement of relative shape distortion, completed by norm information. D. Lhuillier - Séminaire SPhN

  32. Reactor Experiments D. Lhuillier - Séminaire SPhN

  33. Research Reactors Typical reactor core sizes • Compact sources • No oscill. smearing. • High statistics, typically few 100 evts/day/t • Intense source • Very short baselines available (5-50 m) • Alternation of reactor ON/OFF periods • moderate overburden compensated by accurate measurement of the cosmogenic component. • Highly enriched fuel • Well known 235U fisison spectrum. • But challenging reactor-induced backgrounds (g and n) •  Requires comprehensive site characterization. D. Lhuillier - Séminaire SPhN

  34. Main Experimental Parameters All current projects have the sensitivity to test the reactor anomaly space of parameters, Dm2>0.1, sin22q>0.05 Source Detector K.M. Heeger et al., arXiv:1212.2182v1 Year scale stability K.M. Heeger et al., arXiv:1212.2182v1 D. Lhuillier - Séminaire SPhN

  35. Backgrounds Correlated Accidental High E g • Random coinc of independent evts • Accurately measured online using duplicated off-time windows •  Statistical limitation only • Online reduction: overburden, m-veto, PSD of recoiling proton • Measured reactor OFF and subtracted D. Lhuillier - Séminaire SPhN

  36. Worldwide Experimental Program SOLID @ BR2, Belgium Nucifer @ Osiris Saclay DANSS @ KNPP Udolmya Neutrino4 @ SM-3 Dimitrovgrad CARR site Beijing Stereo @ ILL Grenoble US Short Baseline Interest Group Hanaro, Corea D. Lhuillier - Séminaire SPhN

  37. Detection of Reactor n D. Lhuillier - Séminaire SPhN

  38. Reactor νProposals D. Lhuillier - Séminaire SPhN

  39. Gd-Loaded Liquid Scintillators D. Lhuillier - Séminaire SPhN

  40. 70 MW Nucifer @ Osiris Osiris reactor Saclay, France • Detector designed for reactor monitoring studies • 850 kg Gd-loaded LS • ~1000 int. expected / day • Shallow depth (few mwe) 7m D. Lhuillier - Séminaire SPhN

  41. Nucifer: First Neutrinos Detection efficiency and statistical accuracy limited by excessive accidental background Pth (MW) Shallow depth but cosmic bkg is kept below the n signal. D. Lhuillier - Séminaire SPhN

  42. Nucifer: Accidentals External g background: high E rays from n-capture on Fe, Al, Ni, … Nucifer singles prompt delayed • Total rate above 2 MeV = 200 Hz, on specification • But high energy tail, spoiling the n-capture signal around 8 MeV •  Need 4cm extra lead shielding, to be installed soon. D. Lhuillier - Séminaire SPhN

  43. Nucifer: Fast n Background Pulse Shape Discrimination PSD plot of Osiris data taking Qtail Qtot n Nucifer liquid : 50% PXE, 50% dodecane 252Cf source g p recoils Perfect match of p recoils after acc subtraction  No fast neutrons from reactor D. Lhuillier - Séminaire SPhN

  44. Nucifer: Sensitivity to Sterile n • Modest sensitivity to Sterile-n: • Compact core: 60x60x60 cm3 • Short baseline: only 7 m • Simple design • One single baseline • Challenging Reactor bkg • 1 year data taking starting spring 2014 after final shielding upgrade 1 year S/B=0.5 D. Lhuillier - Séminaire SPhN

  45. Stereo @ ILL Outer crown for improved edet and veto of external background Good overburden from water channel, factor 4 attenuation of vertical flux m veto g and n shielding Relative measurement in 6 cells 50 MW core h=80cm, F=40cm Detector based on Double Chooz and Nucifer developments. [8.5-11] m baseline range D. Lhuillier - Séminaire SPhN

  46. Stereo: Background Rejection Core Reduction of accidentals • Comprehensive on site measurements of muon, thermal n, fast n and g backgrounds. • Massive deployment of shielding during the upcoming long reactor shutdown. 30 cm of lead in front hot g spots + hermetic B4C coating. • Dedicated plug of the neutron line. Stereo Shadow of water channel B4C Lead D. Lhuillier - Séminaire SPhN

  47. Stereo: Background Rejection Rejection of fast neutrons 100 ml test sample FoM>1 • Overburden • m-veto and top passive shielding • Active outer-crown • Kinematics and liquid quenching factor  En > 5 MeV • Liquid R&D for optimal light yield and PSD D. Lhuillier - Séminaire SPhN

  48. Stereo Sensitivity • 6 ILL cycles (1.5 year running) • L0 = 9.8 m • S/B = 1.5 • Evis>2 MeV, Neutron cut = 5 MeV • Complete detresponse • dL=20 cm, dE/E~10%@ 1MeV • dEscale = 2% • All syst. of 235U spectrum • 3.5% total norm error • 480 n/day expected • Funded by ANR grant • Time schedule: • 2013-2014: design and construction • Prototype testing • 2015-2016: data taking D. Lhuillier - SéminaireSPhN

  49. Neutrino-4 @ SM3 Courtesy of A. Serebrov • 2.5 m3LS target, 5 section movable detector [6-12] m • 100 MW compact core • Detector at Surface Eprompt>2.2 MeV, No background 95% D. Lhuillier - Séminaire SPhN

  50. Neutrino-4 Prototype Validation of a prototype detector at the WWR-M 17 MW reactor (Gatchina) Raw Raw + veto coinc Coinc + veto • Neutrino detection currently limited by cosmic rays induced fast neutrons. • Lead + CH2 detector shielding integrated at the SM-3 site. • Data taking in 2015 arXiv:1310.5521 D. Lhuillier - Séminaire SPhN

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